Photo-active thermoelectric device



Aug. 13, 1929. w CASE 1,724,872

PHOTO ACTIVE THERMOELECTRIC DEVICE Filed Dec. 22, 1924 Patented Aug. 13,1929.

UNITED STATES PATENT OFFICE THEODORE WILLARD CASE, OF AUBURN, NEW YORK,ASSIGNOR TO CASE RESEARCH. LABORATORY INCORPORATED, OF AUBURN, NEW YORK,A CORPORATION OF NEW YORK.

PHOTO-ACTIVE THERMOELECTRIC DEVICE.

Application filed December 22, 1924. Serial No. 757,524.

This invention relates to a new photoactive thermo-electric device andthe meth 0d of controlling a thermo-ionic current in a vacuum tube by aphoto-active mater1al, and more specifically the invention contemplatesthe control or variation of a thermoelectric current by means of aphoto-electric material that emits electrons when sub JQCtGd to lightrays to thereby assist or counteract or partially counteract the flow ofnegative electrons from the cathode to the anode of a thermo-electricdevice, whereby a variation in the thermo-electric current is effectedproportional to the intensity of the light rays to which thephoto-active mate rial is subjected and this application is acontinuation in part of my application Serial No. 457,283 filed March31, 1921, upon Light Reactive Apparatus, and I have elected to claimherein the device described solely when the photo-active material ismounted upon a non-conductor, and reference is hereby made to myco-pendlng application Serial No. 523,603 which contains the broadclaims to the device herein described without regard to whether thephotoactive material be on a conductor or a nonconductor.

The operation of the structure in accordance with the method hereinafterdescribed is based upon a discovery of the existence of an efiect of aphoto-active material carried by a non-conductor, on a thermo-ioniccurrent in a vacuum tube, whereby the intensity of the light to whichthe photoactive material is subjected may be determined.

The invention adapts itself to various Figure 4 is an illustrationsimilar to Fig ure 3 illustrating a modified form of nonconductor forsupporting the photo-active material.

It is known that if a heated filament and a plate, or other anode beconfined in spaced relation within a vacuum bulb or vessel, the heatedfilament being connected to the negative side of a suitable source ofpotential and the plate or other anode connected to the postive side ofthe source of potential, that a thermo-electric current will flow in thecircuit so formed and from the plate to the filament, the negativeelectrons emitted by the heated filament constituting a currentpath forsuch flow between the plate and filament, and this invention takesadvantage of that known operation of a device of the characterdescribed, in that a photo-electric material adapted to emit electronsunder the action of light is placed within the vacuum bulb or vessel ofsuch a structure in any suitable position therein, and upon anonconducting portion thereof, to thereby control or vary thethermo-electric current in accordance with the intensity of the light ras to which the photo-active material is su jected.

The structure illustrated in Figure 1 comprises a cathode -1 offilamentary form, and a heating circuit therefor, including a source ofpotential 2 and a variable resistance 3. The anode or plate 4 isdisposed within the bulb 5-- in a position spaced from the heatedcathode -1, and a high vacuum is preferably maintained within the bulb5. The cathode 1 and anode -4 are connected in circuit with a source ofpotential 6 and an indicating device, as for instance, a galvanometer 7,the filament 1- being connected to the negative side of the source ofpotential, while the plate 4 is connected to the positive side of thesource of potential.

For the purpose of controlling and varying the thermo-electric currentadapted to flow in the circuit, including the cathode -1' and anode 4, aphoto-active material 9 such as sodium, potassium, barium sub-oxide, isdisposed upon a glass or other non-conducting member 8 which may ofanydesired form and shape, and

supports the photo active material in. aposition adjacent the path ofthe electrons travels ing from the cathode -1- to the plate As shown inFigure 1, the supportis, for instance, a glass pedestal havlng a platelike portion at its top disposed at one side of the path of theelectrons flowing from the heated filament to the anode -4. The

. support for the photo-active material 9 is as stated, a non-conductor,and the photoactive material has no electrlcal connect ons, a itsoperation being solely effected. by the omission of electrons under theinfluence of light and in substantial accordance with the intensity ofthe light to which it is subjected, which electrons assist or counteractthe electrons emitted by the cathode 1, and render the space between thefilament and plate more or less conductive, thereby effecting thecurrent flowing in'the circuit between the filament -1-- and plate 4--in an extent proportional to the intensity of the light to which thephotoactive material is subjected, and this variation in current may beindicated in any suitable manner, as by galvanometer -7.

In Figure 2 instead of supporting the photo-active material 9- upon anon-conductin pedestal or support arising within the bu b ,5-, thephoto-active material is spread or placed upon a portion of the intcrior of the glass bulb 5-, the bulb itself constituting a nonconducting support for the photo-active material, the operation beingthe same as in the construction shown in Figure 1.

In Figure 4: the non-conducting support for the photo-active material,instead of being shown in the form of a plate, as in Figure 1, is showni'nthe form of a glass or othernon-conducting cylinder '-10, theopenin-gthrough thecylinder ermitting free passage of electrons from theheated filament to the plate 4, in that the cylinder surrounds orsubstantially surrounds the path of the electrons travelin from thefilament to the plate, and thelig t reactive material may be spread orotherwise placed or deposited upon the interior of the cylinder.

It will be obvious that altho I have shown and described specific formsof non-conductors for supporting-the photo-active material and specificpositions for its support, that I do not desire to restrict myself tothe details of form or position of the electrodes in the structureillustrated, as thebroad idea of the invention which resides in thecontrol of a thermo-electric current by a photoactive material supportedfrom a non-conductor is, so far as I am aware, novel, and variouschanges in the details of form and arrangement of the parts may be madewithout departing from this invention as set forth in the appendedclaim.

I claim:

A photo-active thermo-electric device comprising a glass bulb housing ananode and a cathode of filamentary form within the bulb, an insulatingmember positioned in the space between the cathode and the anode, and aphoto-active material carried by the insulating member and adapted tovary the current which flows between the anode and the cathodeindependently of the cathodeheating means, and in substantial accordancewith the intensity of the light rays to which it is exposed.

In witness whereof I have hereunto set my hand this 10th day ofDecember, 1924.

THEODORE WILLARD CASE.

